Currently, the liquid crystal display device has been widely used as a display component of electronic devices in various electronic products. The GOA (Gate Driver On Array) circuit is an important part of a liquid crystal display device. The GOA circuit is a technology that uses a process for existing thin film transistor liquid crystal display array to manufacture a gate line scan driving signal circuit on an array substrate to realize a gate-by-gate scan driving method.
The display panel based on Low Temperature Poly-silicon (LTPS) technology can be divided into an NMOS type, a PMOS type and a combination of NMOS and NMOS according to a type of a thin film transistor (TFT) used in the panel. Similarly, the GOA circuit can be divided into a NMOS circuit, a PMOS circuit and a CMOS circuit. The NMOS circuit, in comparison to the CMOS circuit, is of great benefit in terms of improving the yield and reducing cost, due to the omission of PP (P doping, i.e., phosphorus ions doping) mask and process. To develop the stable NMOS circuit has realistic industry needs. In the case of abnormal power off, if the GOA circuit cannot effectively achieve the function of All Gate ON, i.e., all the gate driving signals in the GOA circuit being set to an active potential for scanning the liquid crystal display device simultaneously, the panel will have a ghost image.
For example, taking a forward scan as an example, in the GOA circuit unit shown in FIG. 1, when an abnormal power-off is triggered, if the (n+1)th clock signal accessed to the thin film transistor NT3 is at a high level, the forward scan control signal and the (n+1)th clock signal will be pulled down to a low level simultaneously. As a result, the high potential of the gate of the thin film transistor NT5 is not able to be reset, and thus the thin film transistor NT5 remains turn-on. In the meanwhile, since a thin film transistor NT8 is also on a turn-on state, a high-level signal VGH is superimposed with a low-level signal VGL, and the gate of the thin film transistor NT7 cannot be pulled down completely, causing the thin film transistor NT7 to pull down the gate driving signal G(n) output to the thin film transistor of the pixel unit. The gate driving signal G(n) is thus insufficient to turn on the thin film transistor of the pixel unit, and the charge of the pixel electrode cannot be released in time, resulting in the ghost image occurring in the effective display area during the abnormal power-off.